normal distribution graph/histogram/plot

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Thomas Kozinski on 20 Mar 2021
Edited: Cris LaPierre on 20 Mar 2021
Hello, I am in the process of doing the task and I have encountered a problem with drawing a histogram / graph.
below is the script that will perform the task of n rolls of two cubic dice and calculate the sum of the spots rolled:
count = 0;
for i=1:10
throws1 = randi(6, 1);
throws2 = randi(6, 1);
sumThrow = throws1 + throws2;
end
fprintf('suma : %d\n', sumThrow)
and a function that calculates the expected value and standard deviation:
function [x,y] = external_pdf(mu,sigma)
% [x,y] = external_pdf(mu, sigma)
% mu is expected value
% sigma is standard deviation
% [x,y] = external_pdf(7,2.42)
% plot(x,y)
x = (mu-(3*sigma)):.1:(mu+(3*sigma))
y = 1/(sigma*sqrt(2*pi))*exp(-(x-mu).^2/(2*sigma^2))
end
I tries to draw a normalized histogram and plot a normal distribution graph with the parameters N (7, 2.41), using the command: normfit (7,2.41) - it is supposed to calculate the normal distribution, but when I try to draw it with the histogram command, I get the following drawing, and I'm rather doing something wrong.
below is the content of the task it performs:
Write a script that will do a task n rolls of two cubes and calculate
the total number of pips rolled. Find the expected value and standard deviation. Draw a number of
a calculated histogram and plot a normal distribution plot with parameters N (7, 2.41).
Use the randi, normfit, hist, trapz and plot functions.

Cris LaPierre on 20 Mar 2021
Edited: Cris LaPierre on 20 Mar 2021
Can I assume that this is how you created your histogram?
N = normfit(7,2.41)
N = 7
histogram(N)
It might be worth reviewing what a histogram is. The y axis is a count of the number of data points that fall within each bin. The x axis indicates the bin edges.
Here, N is a single value, 7. So your histogram has a single bin centered at 7, with a height of 1 because 1 value falls within the bin for 7.
If you want a histogram to show a normal distribution, you will need lots of data points, and several bins. For example
nums = randn(1000,1); % 1000 normally distributed random numbers
histogram(nums)